[wintermute-_-]

Not a secret. There's a feature called Smart Photos that you can toggle on and off which basically A/B tests your photos and displays the best performing one first.

[patbutcher]

The key difference is that feature simply places your best performing photo first. The relevance of it leaking an actual number which represents the ratio of right to left swipes is the critical part.

It offers a comparison with other users and the average across all of a users photos probably correlates strongly with the mysterious 'Tinder rating ™'

[georgespencer]

And the fact that it's leaking other user's and not just yours (in fact, in order to get your own you'd need to have two Tinder accounts).